text: // SPDX-License-Identifier: GPL-2.0
  #include <linux/file.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/utime.h>
  #include <linux/syscalls.h>
  #include <linux/uaccess.h>
  #include <linux/compat.h>
  #include <asm/unistd.h>
  
  static bool nsec_valid(long nsec)
  {
  	if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
  		return true;
  
  	return nsec >= 0 && nsec <= 999999999;
  }
  
  static int utimes_common(const struct path *path, struct timespec64 *times)
  {
  	int error;
  	struct iattr newattrs;
  	struct inode *inode = path->dentry->d_inode;
  	struct inode *delegated_inode = NULL;
  
  	error = mnt_want_write(path->mnt);
  	if (error)
  		goto out;
  
  	if (times && times[0].tv_nsec == UTIME_NOW &&
  		     times[1].tv_nsec == UTIME_NOW)
  		times = NULL;
  
  	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
  	if (times) {
  		if (times[0].tv_nsec == UTIME_OMIT)
  			newattrs.ia_valid &= ~ATTR_ATIME;
  		else if (times[0].tv_nsec != UTIME_NOW) {
  			newattrs.ia_atime = times[0];
  			newattrs.ia_valid |= ATTR_ATIME_SET;
  		}
  
  		if (times[1].tv_nsec == UTIME_OMIT)
  			newattrs.ia_valid &= ~ATTR_MTIME;
  		else if (times[1].tv_nsec != UTIME_NOW) {
  			newattrs.ia_mtime = times[1];
  			newattrs.ia_valid |= ATTR_MTIME_SET;
  		}
  		/*
  		 * Tell setattr_prepare(), that this is an explicit time
  		 * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
  		 * were used.
  		 */
  		newattrs.ia_valid |= ATTR_TIMES_SET;
  	} else {
  		newattrs.ia_valid |= ATTR_TOUCH;
  	}
  retry_deleg:
  	inode_lock(inode);
  	error = notify_change(path->dentry, &newattrs, &delegated_inode);
  	inode_unlock(inode);
  	if (delegated_inode) {
  		error = break_deleg_wait(&delegated_inode);
  		if (!error)
  			goto retry_deleg;
  	}
  
  	mnt_drop_write(path->mnt);
  out:
  	return error;
  }
  
  /*
   * do_utimes - change times on filename or file descriptor
   * @dfd: open file descriptor, -1 or AT_FDCWD
   * @filename: path name or NULL
   * @times: new times or NULL
   * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
   *
   * If filename is NULL and dfd refers to an open file, then operate on
   * the file.  Otherwise look up filename, possibly using dfd as a
   * starting point.
   *
   * If times==NULL, set access and modification to current time,
   * must be owner or have write permission.
   * Else, update from *times, must be owner or super user.
   */
  long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
  	       int flags)
  {
  	int error = -EINVAL;
  
  	if (times && (!nsec_valid(times[0].tv_nsec) ||
  		      !nsec_valid(times[1].tv_nsec))) {
  		goto out;
  	}
  
  	if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
  		goto out;
  
  	if (filename == NULL && dfd != AT_FDCWD) {
  		struct fd f;
  
  		if (flags)
  			goto out;
  
  		f = fdget(dfd);
  		error = -EBADF;
  		if (!f.file)
  			goto out;
  
  		error = utimes_common(&f.file->f_path, times);
  		fdput(f);
  	} else {
  		struct path path;
  		int lookup_flags = 0;
  
  		if (!(flags & AT_SYMLINK_NOFOLLOW))
  			lookup_flags |= LOOKUP_FOLLOW;
  		if (flags & AT_EMPTY_PATH)
  			lookup_flags |= LOOKUP_EMPTY;
  retry:
  		error = user_path_at(dfd, filename, lookup_flags, &path);
  		if (error)
  			goto out;
  
  		error = utimes_common(&path, times);
  		path_put(&path);
  		if (retry_estale(error, lookup_flags)) {
  			lookup_flags |= LOOKUP_REVAL;
  			goto retry;
  		}
  	}
  
  out:
  	return error;
  }
  
  SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
  		struct __kernel_timespec __user *, utimes, int, flags)
  {
  	struct timespec64 tstimes[2];
  
  	if (utimes) {
  		if ((get_timespec64(&tstimes[0], &utimes[0]) ||
  			get_timespec64(&tstimes[1], &utimes[1])))
  			return -EFAULT;
  
  		/* Nothing to do, we must not even check the path.  */
  		if (tstimes[0].tv_nsec == UTIME_OMIT &&
  		    tstimes[1].tv_nsec == UTIME_OMIT)
  			return 0;
  	}
  
  	return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
  }
  
  #ifdef __ARCH_WANT_SYS_UTIME
  /*
   * futimesat(), utimes() and utime() are older versions of utimensat()
   * that are provided for compatibility with traditional C libraries.
   * On modern architectures, we always use libc wrappers around
   * utimensat() instead.
   */
  static long do_futimesat(int dfd, const char __user *filename,
  			 struct __kernel_old_timeval __user *utimes)
  {
  	struct __kernel_old_timeval times[2];
  	struct timespec64 tstimes[2];
  
  	if (utimes) {
  		if (copy_from_user(&times, utimes, sizeof(times)))
  			return -EFAULT;
  
  		/* This test is needed to catch all invalid values.  If we
  		   would test only in do_utimes we would miss those invalid
  		   values truncated by the multiplication with 1000.  Note
  		   that we also catch UTIME_{NOW,OMIT} here which are only
  		   valid for utimensat.  */
  		if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
  		    times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
  			return -EINVAL;
  
  		tstimes[0].tv_sec = times[0].tv_sec;
  		tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
  		tstimes[1].tv_sec = times[1].tv_sec;
  		tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
  	}
  
  	return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
  }
  
  
  SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
  		struct __kernel_old_timeval __user *, utimes)
  {
  	return do_futimesat(dfd, filename, utimes);
  }
  
  SYSCALL_DEFINE2(utimes, char __user *, filename,
  		struct __kernel_old_timeval __user *, utimes)
  {
  	return do_futimesat(AT_FDCWD, filename, utimes);
  }
  
  SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
  {
  	struct timespec64 tv[2];
  
  	if (times) {
  		if (get_user(tv[0].tv_sec, &times->actime) ||
  		    get_user(tv[1].tv_sec, &times->modtime))
  			return -EFAULT;
  		tv[0].tv_nsec = 0;
  		tv[1].tv_nsec = 0;
  	}
  	return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
  }
  #endif
  
  #ifdef CONFIG_COMPAT_32BIT_TIME
  /*
   * Not all architectures have sys_utime, so implement this in terms
   * of sys_utimes.
   */
  #ifdef __ARCH_WANT_SYS_UTIME32
  SYSCALL_DEFINE2(utime32, const char __user *, filename,
  		struct old_utimbuf32 __user *, t)
  {
  	struct timespec64 tv[2];
  
  	if (t) {
  		if (get_user(tv[0].tv_sec, &t->actime) ||
  		    get_user(tv[1].tv_sec, &t->modtime))
  			return -EFAULT;
  		tv[0].tv_nsec = 0;
  		tv[1].tv_nsec = 0;
  	}
  	return do_utimes(AT_FDCWD, filename, t ? tv : NULL, 0);
  }
  #endif
  
  SYSCALL_DEFINE4(utimensat_time32, unsigned int, dfd, const char __user *, filename, struct old_timespec32 __user *, t, int, flags)
  {
  	struct timespec64 tv[2];
  
  	if  (t) {
  		if (get_old_timespec32(&tv[0], &t[0]) ||
  		    get_old_timespec32(&tv[1], &t[1]))
  			return -EFAULT;
  
  		if (tv[0].tv_nsec == UTIME_OMIT && tv[1].tv_nsec == UTIME_OMIT)
  			return 0;
  	}
  	return do_utimes(dfd, filename, t ? tv : NULL, flags);
  }
  
  #ifdef __ARCH_WANT_SYS_UTIME32
  static long do_compat_futimesat(unsigned int dfd, const char __user *filename,
  				struct old_timeval32 __user *t)
  {
  	struct timespec64 tv[2];
  
  	if (t) {
  		if (get_user(tv[0].tv_sec, &t[0].tv_sec) ||
  		    get_user(tv[0].tv_nsec, &t[0].tv_usec) ||
  		    get_user(tv[1].tv_sec, &t[1].tv_sec) ||
  		    get_user(tv[1].tv_nsec, &t[1].tv_usec))
  			return -EFAULT;
  		if (tv[0].tv_nsec >= 1000000 || tv[0].tv_nsec < 0 ||
  		    tv[1].tv_nsec >= 1000000 || tv[1].tv_nsec < 0)
  			return -EINVAL;
  		tv[0].tv_nsec *= 1000;
  		tv[1].tv_nsec *= 1000;
  	}
  	return do_utimes(dfd, filename, t ? tv : NULL, 0);
  }
  
  SYSCALL_DEFINE3(futimesat_time32, unsigned int, dfd,
  		       const char __user *, filename,
  		       struct old_timeval32 __user *, t)
  {
  	return do_compat_futimesat(dfd, filename, t);
  }
  
  SYSCALL_DEFINE2(utimes_time32, const char __user *, filename, struct old_timeval32 __user *, t)
  {
  	return do_compat_futimesat(AT_FDCWD, filename, t);
  }
  #endif
  #endif
  